The effect of surgical washers used with olive K-wires on bone surface kinetics in external fixation: a biomechanical study

Objectives: In external fixation, the type and configuration of K-wires have a considerable effect on fixation stability. Indications for external fixation have recently increased in the treatment of various musculoskeletal pathologies in os-teoporotic patients. This biomechanical study was designed to determine the effect of surgical washers used with olive wires on surface kinetics of the cortical bone. Methods: The study included 32 tibiae obtained from one-year-old sheep. Samples were prepared from the proximal parts of the tibiae which were then divided into four groups equal in number. A 1.8-mm olive K-wire was inserted into the proximal metaphyseal regions of the tibiae. Except for the control group, surgical washers were used with olive K-wires in the three study groups, with diameters of 5 mm, 7 mm, and 10 mm, respectively. The samples were then placed in a specially designed servo-hydraulic universal testing machine for static tensile test at 10 mm/min. Results: The mean failure load was 806.9 N in the control group, compared to 1285.9 N, 1317.9 N, and 1345.9 N in the three groups in which 5-mm, 7-mm, and 10-mm surgical washers were used, respectively. While there were significant differences between the control and study groups (p<0.0001), failure loads did not differ significantly between the three study groups (p=0.574). Conclusion: The use of surgical washers in combination with olive K-wires offers a significant advantage to increase stability and to decrease surface pressure. We recommend utilization of washers for external fixation surgery in os-teoporotic patients and osteoporotic bone segments.